This invention relates generally to converting radar scan data vectors to a video display and, more particularly, to apparatus of the type described for use with a high resolution, motion stabilizing radar display having multiresolution display raster output capabilities for eliminating artifacts attributed to raster image update.
Current requirements for scan converters of the type contemplated include converting radar data vectors up to 960 pixels in length at an angular rate of 90 degrees per second. A complete 360 degree radar scan must be maintained in memory. Further, the apparatus must output approximately a 1024.times.1024 raster image of arbitrary position and angular orientation with respect to the radar scan maintained in memory, whereby motion stabilization is made possible.
Due to bandwidth limitations of vector address generators used in apparatus of the type described a raster image frame update rate is approximately 15 Hz, which is relatively slow. This produces undesirable scan artifacts during a first sweep, or when the scan data changes significantly from the previous sweep.
The present invention overcomes this disadvantage by incorporating multiresolution output features into the disclosed apparatus. More specifically, the resolution of the output image is reduced by one-half in both the horizontal and vertical directions. This reduced resolution mode of the invention increases the effective raster image frame update rate by almost four times, thereby eliminating all scan artifacts occurring from the aforenoted relatively slow raster image frame update rate.
It will be understood that the reduced resolution mode of the invention is intended to be used during any radar scan where previous raster image frame data is erased, or is significantly different than current data. Subsequent correlated scans are then displayed in full (high) resolution. The reduced resolution mode can also be used in any other case where current raster image frame data has significantly changed in orientation, position or content from the previous data.